Abstract Summary
The offshore wind industry is expanding rapidly due to the high demand for sustainable energy. Large wind farms are planned in the European seas in the coming decade, and because of that, concerns for environmental harm arise. The most significant environmental impact is during the foundation pile installation, when traditionally, an impact hammer drives the pile into the soil, causing high underwater noise levels. New techniques arise in trying to omit high noise levels during installation. One of the promising techniques is 'Gentle Driving of Piles' (GDP). GDP uses an axial vibratory hammer combined with a high-frequency torsional vibratory hammer, reducing the friction and energy needed to drive the pile. The pile-soil friction couples the axial and torsional driving mechanisms. Therefore, modelling the interface and the soil is crucial for accurate noise predictions. This study focuses on noise predictions for piles driven by GDP. A linearized friction element is introduced to describe pile-soil interaction based on the output from a driveability model. Linearization of the interface conditions is essential to keep the computational time low. This paper presents a study on the effect of the modelled interface condition for large and small pile foundations. Driving depth and soil conditions are varied to show the possible noise levels in varying cases. Finally, the coupling between vertical and torsional excitation is examined.
